Running in the Cold: Good or Bad for Your Health?

“You’re going running in this weather? You’re crazy. You’ll get sick, and exercising in these conditions is really bad for you!” Mum’s advice, or your partner’s, probably comes from the best of intentions: protecting you from the terrible danger winter supposedly poses to your fragile little body. But it isn’t particularly well founded. While people who don’t take part in outdoor sports may worry about getting ill or harming their health by exhausting themselves outdoors in winter, the cold isn’t the enemy many believe it to be.

The cold, yes, but how cold?

“The cold in Western Europe isn’t a problem because it’s not extreme,” says Guillaume Millet, PhD in exercise physiology and an ultra-endurance expert. “Problems start below -15°C.” Such conditions are relatively rare in France and affect very few athletes. People living in the mountains may encounter these temperatures, but even there they remain exceptional. In Western Europe, the cold we usually face therefore poses no real threat to our health.

The cold is a red herring

When we’re exposed to the cold, our bodies adapt to keep our temperature around 37°C. This process is known as thermogenesis.

• The blood vessels beneath the skin constrict, a process known as vasoconstriction, reducing blood flow and limiting heat loss

• The heart’s oxygen needs increase, while the muscles receive less blood flow.

• We shiver, and our hairs stand on end to create a thin layer of warm air against the skin

• Breathing and urine production change

• Energy expenditure increases

All these responses form the body’s strategy for generating heat in difficult weather conditions. So why limit physical activity when the effort itself produces heat? “You warm up quickly when you run. The only precaution is to cover your extremities, namely your hands, feet and head,” says Guillaume Millet.

In practical terms, you shouldn’t head out into the snow or sub-zero temperatures in shorts and a T-shirt. Dress appropriately so you’re warm enough, without piling on so many layers that you end up drenched in sweat. The best way to tell whether you’re dressed suitably for a winter run is to feel slightly cold when you leave home and during the first 10 minutes of your run. If you feel the cold particularly badly, set off a little overdressed and remove a layer as soon as you start overheating. Wear gloves, a hat or headband, and good socks.

As for the supposed increase in energy expenditure caused by thermogenesis, it’s minimal: just 5 to 10% of your overall resting calorie expenditure. When you run, your body temperature rises, so you stop shivering and no longer spend that additional energy. The extra calories burned then come from the exercise itself, not thermogenesis. Exercising in the cold is therefore not a problem. Quite the opposite!

Repeated hard efforts in bitter cold are a different story

Aside from the extreme conditions we’ve already mentioned, namely temperatures below -15°C, repeated efforts in the cold can become harmful to your health. “One potential problem arises when an athlete regularly trains in the cold, as cross-country skiers and biathletes do,” explains Guillaume Millet. “Many cross-country skiers are actually prescribed Ventolin to treat asthma brought on by repeated training in the cold.”

The lungs are the organ most exposed when the air is cold and dry. One solution is to breathe through a “mask”, such as a neck gaiter pulled up over the nose. Runners who are frequently exposed to the cold, particularly those who live and train in the mountains year-round, would do well to adopt this strategy.

So, unless you’re dealing with extreme conditions or a particularly demanding training environment, the cold isn’t nearly as dangerous as the myths suggest, or as your ever-worried mum insists. Dress appropriately and you can run through the winter in France without fear, as long as you watch out for other hazards, such as black ice, which can lead to some painful acrobatics!